In conventional gasoline engines, in order to fix a crankshaft in relation to the longitudinal direction of an engine, a bearing cap is typically mounted underneath a cylinder block, in comparison with a camshaft using a cam cap at a top portion of a cylinder head.
Due to tolerance, production errors, manufacturing defects, and other various factors that may occur in an engine, the crankshaft and the camshaft should not be fixed by using all bearing caps and cam caps in the longitudinal direction of an engine. Therefore, only some of the bearing caps and cam caps are allowed to have a thrust bearing structure in order to firmly restrict a certain part of the crankshaft and the camshaft.